Fuel injection valve

ABSTRACT

A fuel injection valve is provided with a main body and a valve member. The main body has a fuel passage and a fuel injection opening formed at the downstream-end of the fuel passage. The valve member is provided in the fuel passage. The valve member is configured to move between a first position in which the valve member closes the fuel injection opening and a second position in which the valve member opens the fuel injection opening. The fuel injection valve is further provided with a compression spring disposed in the fuel passage and a spring pin. The compression spring restrains the valve member toward the first position. The spring pin is pressedly inserted into the fuel passage for keeping the compression spring in the fuel passage. A surface of the spring pin has a resistance against sulfur.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2007-183527, filed on Jul. 12, 2007, the contents of which are hereby incorporated by reference into the present specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel injection valve, particularly to a fuel injection valve which injects fuel into an internal combustion engine.

2. Description of the Related Art

U.S. Pat. No. 5,165,656A discloses a fuel injection valve which injects fuel into an internal combustion engine. This fuel injection valve is provided with a main body and a valve member. The main body has a fuel passage and a fuel injection opening formed at the downstream-end of the fuel passage. The valve member is disposed in the fuel passage and is constructed so as to move between a first position in which the valve member shuts the fuel injection opening and a second position in which the valve member opens the fuel injection opening. The fuel injection valve is further provided with a compression spring and an actuator. The compression spring is disposed in the fuel passage and biases the valve member toward the first position. The actuator moves the valve member toward the second position against bias force of the compression spring. The actuator is constructed by using an electromagnetic coil.

A spring pin (called an adjustment bushing in the above literature) is arranged in the fuel passage of the main body. The spring pin is pressed into the fuel passage for keeping the compression spring in the fuel passage. The above literature describes that anti-rust spring steel, bronze, brass, tombac and copper beryllium are useful as material of which the spring pin is made.

BRIEF SUMMARY OF THE INVENTION

Since the spring pin is exposed to the fuel which passes through the fuel passage, the spring pin is required to have a corrosion resistance against fuel. Therefore, material having excellent characteristic of corrosion resistance against fuel is used for the material of which the spring pin is made. However, in the conventional fuel injection valve, it is confirmed that corrosion of the spring pin progresses at an abnormal speed and the functions of the fuel injection valve are lowered at an early stage. There is a need for finding the cause of the above problem and a need for a fuel injection valve taking countermeasures against the problem.

The inventor of the present invention eagerly pursued the above problem and found that the cause of the problem is in the quality of the fuel. For example, to an automobile in which the fuel injection valve is installed, petroleum (fuel) is repeatedly supplied in unspecified gas stations. Therefore, the quality of the fuel supplied to the automobile is not always constant. There may be a case sometimes where fuel with inferior quality is supplied to the automobile. The fuel with inferior quality often includes a large amount of sulfur. In the case where the fuel with such an inferior quality is frequently supplied, sulfidation corrosion of the spring pin is unavoidably advanced at an abnormal speed. It is found by the inventor of the present invention that the abnormal corrosion of the spring pin is caused by the sulfidation corrosion due to sulfur included in the fuel. Based on the aforesaid finding, the possibility of effectively preventing the abnormal corrosion of the spring pin has been realized by giving a resistance against sulfur to a surface of the spring pin.

A fuel injection valve realized by the present teachings is provided with a main body and a valve member. The main body has a fuel passage and a fuel injection opening formed at the downstream-end of the fuel passage. The valve member is disposed in the fuel passage and is constructed so as to move between a first position in which the valve member shuts the fuel injection opening and a second position in which the valve member opens the fuel injection opening.

The fuel injection valve is further provided with a compression spring and a spring pin. The compression spring is disposed in the fuel passage, and biases the valve member towards the first position. The spring pin is tightly inserted into the fuel passage for keeping the compression spring in the fuel passage. The spring pin is made of material having a resistance against sulfur, preferably a copper alloy having a resistance against sulfur.

In the fuel injection valve according to the present teachings, the spring pin is made of material having the resistance against sulfur. Therefore, even in the case where fuel which includes a relatively large amount of sulfur, as such as the fuel with inferior quality, is used, the corrosion of the spring pin is effectively suppressed. Thereby, the functions of the fuel injection valve are maintained over a longer time period.

The spring pin is preferably made of a copper alloy containing at least one of nickel, silicon, aluminum, and chromium by at least 5 percent by weight.

This type of copper alloy is remarkably invulnerable to corrosion caused by sulfur. Therefore, the spring pin made of this type of copper alloy is able to suppress the corrosion of the spring pin remarkably.

The spring pin is more preferably made of albata; a copper alloy mainly composed of copper, nickel, and zinc.

After being tightly pressed into the fuel passage, the position of the spring pin needs to be stably maintained against the bias force from the compression spring. Therefore, the spring pin is required to have sufficient strength and to be strongly fitted into the fuel passage. Albata has the favorable resistance against sulfur as well as the sufficient strength. Therefore, the spring pin made of albata is able to restrain the corrosion of the spring pin and is able to be tightly fitted into the fuel passage.

In another fuel injection valve realized by the present teachings, the surface of the spring pin may be covered with a film having a resistance against sulfur. In this fuel injection valve, the corrosion of the spring pin due to sulfur may also be suppressed and its functions may be maintained over a longer time period.

The above film having a resistance against sulfur may preferably be a Ni—P alloy plated layer. The Ni—P alloy plated layer has an employable corrosion resistance against sulfur. By forming the Ni—P alloy plated layer on the surface of the spring pin, it is possible to remarkably hinder the corrosion of the spring pin.

An exterior surface of the spring pin may preferably be roughened. In employing the material of the spring pin based on the present teachings, there may be a case where the force required for pressing the spring pin into the fuel passage increases. In this case, with the exterior surface of the spring pin being roughened, it is possible to reduce the force required for fitting the spring pin into the fuel passage.

The above roughening treatment may preferably be a shot peening treatment. By utilizing the shot peening treatment, proper roughening of the exterior surface of the spring pin can be done in a relatively easy process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a fuel injection valve.

FIG. 2 shows a state in which a valve member is at a first position.

FIG. 3 shows a state in which the valve member is at a second position.

FIG. 4 is a perspective view of a spring pin.

DETAILED DESCRIPTION OF THE DRAWINGS

Some of the characteristic features of an embodiment in which the present invention may be carried out are listed below.

(Feature 1) A main body may be provided with a body, a core fixed in the body, and a valve seat fixed at one end of the body and provided with a fuel injection opening. A valve member which may be disposed in the main body may be formed between the core and the valve seat. The valve member may be constructed so as to move between a first position in which one end of the valve member is brought in abutment with the valve seat so as to shut the fuel injection opening and a second position in which one end of the valve member is brought apart from the valve seat and the other end is brought in abutment with the core.

(Feature 2) A shutter portion which is brought in abutment with the valve seat so as to shut the fuel injection opening may be provided in one end of the valve member.

(Feature 3) An actuator may be constructed by using an electromagnetic coil. The core and the valve member may be formed by using magnetic material. In a case where electricity is provided to the electromagnetic coil, the core and the valve member are magnetized.

(Feature 4) The spring pin may be a hollow cylindrical member and may be provided with a slit which extends in the longitudinal direction.

EMBODIMENT OF THE INVENTION

An unlimiting embodiment of a fuel injection valve actualized with the present teachings will be described with reference to the drawings. FIG. 1 shows a vertical sectional view of a fuel injection valve 10 of the embodiment. As shown in FIG. 1, the fuel injection valve 10 is provided with a main body 12, a valve member 30, a compression spring 24 and an electromagnetic coil 26.

Inside the main body 12, a fuel passage 20 through which the fuel passes is formed. An arrow A in FIG. 1 shows the flowing direction of the fuel. At the downstream-end 12d of the main body 12, a fuel injection opening 42 is formed. Further upstream to the upstream-end 12c of the main body 12, a fuel pipe (not shown) which extends from a fuel tank (not shown) is connected. The fuel passage 20 is communicates the fuel injection opening 42 and the upstream-end 12c of the main body 12.

In the present specification, the expression “upstream” means upstream with regard to the fuel flowing direction A, and the expression “downstream” means downstream with regard to the fuel flowing direction A. That is, the expressions “upstream side” and “downstream side” correspond to the “upper side” and the “lower side” as shown in FIG. 1 respectively.

A configuration of the main body 12 will be described in detail. As shown in FIG. 1, the main body 12 is provided with a body 14, a core 16, a spring pin 22, a valve seat holder 32 and a valve seat 34.

The body 14 is a cylindrical member which constructs an outer frame of the main body 12. The body 14 is made of resin. On an exterior surface of the body 14, a connector 48 which is connected to an external control unit (not shown) is formed. In the connector 48, a plurality of terminal pins 50 which are electrically connected to the electromagnetic coil 26 are formed.

The core 16 is a hollow cylindrical member which is made of magnetic material, and is fixed to a through hole 14 a of the body 14. A part of the core 16 protrudes from the through hole 14 a of the body 14 to the upstream side. That is, a part of the core 16 rises out in the upstream direction from the uppermost edge of the body 14. The downstream-end 16 d of the core 16 is arranged within the through hole 14 a of the body 14 at the downstream side. A through hole 16 a formed inside the core 16 constructs a part of the fuel passage 20. In the through hole 16 a of the core 16, a filter 18 for removing a foreign substance from the fuel is provided. The core 16 is formed on the opposite side of fuel injection opening 42 with regard to the valve member 30. It can also be said that the core 16 is formed on the upstream side of the valve member 30, while the fuel injection opening 42 is formed on the downstream side of the valve member 30.

The spring pin 22 is a hollow cylindrical member of which a through hole 22 a is formed in the midst. The spring pin 22 thus has an exterior surface on the outside of the spring pin 22, and an interior surface on the inside of the through hole 22 a. The through hole 22 a constructs a part of the fuel passage 20. The spring pin 22 is pressedly inserted into the through hole 16 a of the core 16. In such condition, the exterior surface of the spring pin 22 makes tight contact with the surface of the through hole 16 a (that is, the interior surface of the core 16). The spring pin 22 is arranged on the upstream side of the compression spring 24, and is abutted with the upstream-end 24 c of the compression spring 24. The spring pin 22 is for adjusting the amount to which the compression spring 24 is to be compressed. The degree of compression of the compression spring 24 can be changed by changing the position into which the spring pin 22 is inserted. The inserting position of the spring pin 22 can also be described as the depth to which the spring pin is thrust into towards the downstream-end 16 d of the core 16. The spring pin 22 will be described further in detail later.

The valve seat holder 32 is a cylindrical member with a through hole 32 a formed in the midst thereof. The valve seat holder 32 is fixed into the through hole 14 a of the body 14. The valve seat holder 32 is formed on the downstream side of the core 16, and a part of the valve seat holder 32 protrudes from the through hole 14 a of the body 14 towards the downstream side. Inside the through hole 32 a of the valve seat holder 32, the valve member 30 is disposed. A clearance is formed between the interior surface of the through hole 32 a of the valve seat holder 32 and the valve member 30. The clearance formed thereof constructs a part of the fuel passage 20. The clearance may be partially formed among the border between the through hole 32 a and the valve member 30. At the upstream-end of the valve seat holder 32, a cylindrical sleeve 28 made of non-magnetic material is provided. A through hole 28 a is formed in the midst of the cylindrical sleeve 28. In the through hole 28 a of the sleeve 28, the downstream-end 16 d of the core 16 and the upstream-end 30 c of the valve member 30 are inserted. The valve member 30 is slidably arranged with regard to the interior side surface of the through hole 28 a of the sleeve 28.

The valve seat 34 is a cylindrical member and is fixed into the through hole 32 a of the valve seat holder 32. A cavity 34 b is formed inside the valve seat 34 with a bottom surface residing on the downstream side. A through hole 34 a is formed on the bottom surface of the valve seat 34. The downstream part of the valve member 30 is arranged inside the internal cavity 34 b of the valve seat 34. A clearance is formed between the interior side and bottom surfaces of the cavity 34 b of the valve seat 34 and the valve member 30. The clearance formed thereof constructs a part of the fuel passage 20. Over a part of an exterior surface of the valve seat 34 at its downstream side, an orifice plate 38 is provided. A through hole 38 a is formed on the orifice plate 38 at a location that corresponds to the position at which the through hole 34 a is formed on the valve seat 34. The valve seat 34 and the orifice plate 38 are formed at the downstream-end 12 d of the main body 12. Of the valve seat 34 and the orifice plate 38, through holes 34 a and 38 a construct the fuel injection opening 42.

Next, a construction of the valve member 30 will be described more in detail. The valve member 30 is a cylindrical member made of magnetic material. The valve member 30 is hollowly formed, with a bottom surface residing on the downstream side; a through hole 30 a is formed within the valve member 30. The valve member 30 is disposed in the through hole 32 a of the valve seat holder 32, and is slidably supported so as to slide in the direction parallel to the fuel flowing direction A. The downstream-end 24 d of the compression spring 24 is abutted with the valve member 30.

The upstream-end 30 c of the valve member 30 faces the downstream-end 16 d of the core 16 which serves as a part of the main body 12. At the downstream-end of the valve member 30, a plug portion 36 for closing the fuel injection opening 42 is provided. The internal through hole 30 a of the valve member 30 is communicated with the through hole 16 a of the core 16, and constructs a part of the fuel passage 20. On the lower side surface of the valve member 30, a plurality of through holes 30 b is formed. The plurality of through holes 30 b align orthogonal to the fuel flowing direction between the internal through hole 30 a and the plug portion 36. The internal through hole 30 a of the valve member 30 is communicated with the internal hole 34 b of the valve seat 34 through the aforementioned through holes 30 b.

The valve member 30 is configured to move between a first position in which the valve member 30 shuts the fuel injection opening 42 as shown in FIG. 2, and a second position in which the valve member 30 opens the fuel injection opening 42 as shown in FIG. 3. It should be noted that the first position is the limit to which the valve member 30 is able to move towards the downstream side; approaching the side of the fuel injection opening 42, and the second position is the limit to which the valve member 30 is able to move towards the upstream side; receding from the side of the fuel injection opening 42. In the case where the valve member 30 is at the first position as shown in FIG. 2, the plug portion 36 serving as the downstream-end of the valve member 30 is brought in contact with the valve seat 34 so as to close the fuel injection opening 42. At this moment, the upstream-end 30 c of the valve member 30 is parted from the downstream-end 16 d of the core 16. Meanwhile, in the case where the valve member 30 is at the second position as shown in FIG. 3, the plug portion 36 serving as the downstream-end of the valve member 30 is brought apart from the valve seat 34 so as to open the fuel injection opening 42. At this moment, the upstream-end 30 c of the valve member 30 is in contact with the downstream-end 16 d of the core 16.

Next, the details of the configurations of the compression spring 24 and the electromagnetic coil 26 will be described. As aforementioned, the compression spring 24 is disposed in the through hole 16 a of the core 16. The compression spring 24 is formed between the spring pin 22 and the valve member 30, in a state that the compression spring 24 is compressed. The upstream-end 24 c of the compression spring 24 is abutted with the exterior bottom surface of the spring pin 22, and the downstream-end 24 d of the compression spring 24 is abutted with a surface protruding within the through hole 30 a of the valve member 30. The compression spring 24 biases the valve member 30 towards the first position by its elastic force, which is the movement limit in the downstream direction (refer to FIG. 2).

The electromagnetic coil 26 is fixed in the through hole 14 a of the body 14. The electromagnetic coil 26 surrounds part of the core 16 including the downstream-end 16 d. Electricity is provided to the electromagnetic coil 26 from the external control unit (not shown) through the terminal pins 50 of the connector 48. The electricity is provided at the timing at which the fuel is to be injected. The electromagnetic coil 26 generates a magnetic field by the electricity provided thereto.

Next, The manner in which the fuel injection valve 10 operates will be described. Fuel flows from the fuel pipe (not shown) which is connected to the upstream-end 12 c into the main body 12 of the fuel injection valve 10. The flowing fuel flows through the fuel passage 20 and reaches the fuel injection opening 42 formed at the downstream-end 12 d of the main body 12. In the case where the electricity is not provided to the electromagnetic coil 26, the valve member 30 is maintained at the first position by the bias force of the compression spring 24 (refer to FIG. 2). In this case, since the fuel injection opening 42 is shut by the plug portion 36 of the valve member 30, the fuel is not injected from the fuel injection opening 42.

Meanwhile, when the electricity is turned on and provided to the electromagnetic coil 26, the electromagnetic coil 26 generates a magnetic field, thus magnetizing the core 16 and the valve member 30. In such condition, the core 16 and the valve member 30 attract each other such that the valve member 30 shifts its posture to the second position, moving upward against the bias force of the compression spring 24 (refer to FIG. 3). The plug portion 36 of the valve member 30 is brought apart from the valve seat 34, such that the fuel injection opening 42 is opened. At this moment, the fuel is injected from the fuel injection opening 42. The electricity is intermittently provided to the compression spring 24 and the fuel is intermittently injected from the fuel injection opening 42.

The schematic structure and operation of the fuel injection valve 10 of the present embodiment is described above. Next, a detailed description of the configuration of the spring pin 22 will be described.

FIG. 4 shows a single body of the spring pin 22. As shown in FIG. 4, a slit 22e which extends in the longitudinal direction is formed in the spring pin 22. An exterior surface 22 f of the spring pin 22 is to be tightly in contact with the interior surface of the core 16. The exterior surface 22 f is roughened by shot peening treatment so as to be an remarkably uneven and rough surface. When the exterior surface 22 f of the spring pin 22 is uneven and rough, it is possible to reduce the pressing force required at the time of pressing the spring pin 22 into the through hole 16 a of the core 16. It should be noted that the exterior surface 22 f of the spring pin 22 can be formed as an uneven surface by roll dicing or the like with using a pattern die for transferring the unevenness.

The spring pin 22 is repeatedly exposed to the fuel which passes through the through hole 16 a of the core 16. The spring pin 22 needs to be able to tolerate corrosion that may be caused by the fuel. Thus, a corrosion resistance against fuel is essential to the spring pin 22. As the quality of the fuel to be used may not always be of a high standard, and there may be a case where the fuel includes a large amount of foreign substance such as inferior gasoline, and LPG may be used. Accordingly, the spring pin 22 is also required to have a high corrosion resistance against such foreign substance included in the fuel.

The present inventor has confirmed that abnormal corrosion of the spring pin 22 is caused particularly due to sulfur among the foreign substance included in the fuel. Sulfide generated by sulfidation corrosion of the spring pin 22 easily accumulates between the valve member 30 and the valve seat 34, often causing defect in closing the fuel injection opening 42. As a result of experimenting the corrosion resistance against sulfur (a tolerance against sulfur) of various materials, the present inventor has confirmed that a copper alloy containing at least one of nickel, silicon, aluminum, and chromium by at least 5 percent by weight has the favorable corrosion resistance against sulfur (a favorable tolerance against sulfur). These elements easily react with an oxygen ion in the air or in the fuel, and the layer of their oxidized film(s) is easily formed on the surface of the spring pin 22 covering the surface thereof. Particularly, when one or more of these elements are contained by at least 5 percent by weight, their oxidized film(s) is sufficiently formed on the surface of the spring pin 22 so as to significantly retard the corrosion of the spring pin 22 due to sulfur. Accordingly, when the spring pin 22 is made of a copper alloy containing at least one of nickel, silicon, aluminum, and chromium by at least 5 percent by weight, even in the case where the fuel with inferior quality is frequently utilized, for example, the corrosion of the spring pin 22 is even more effectively suppressed, and functions of the fuel injection valve 10 can be maintained for a longer time period. That is, rise of the problem such as the defect in hindering the fuel injection opening 42 to close caused by the accumulated sulfide between the valve member 30 and the valve seat 34 may be prevented. Furthermore, a decrease in the fuel injection amount caused by the accumulated sulfide in the fuel injection opening 42 may also be prevented.

A copper alloy containing at least one of nickel, silicon, aluminum, and chromium by at least 5 percent by weight may include, cupronickel (containing 9 to 11 weight percent of nickel) and albata (containing 16.5 to 19.5 weight percent of nickel), for example. It should be noted that a relatively large amount of zinc may also be included in albata (approximately 20 percent by weight).

In the present embodiment, the spring pin 22 is made of albata. Albata has a favorable resistance against sulfur as well as relatively high strength as in having a high scale of Young's modulus. Therefore, the spring pin 22 which is made of albata may be strongly fitted to the through hole 16 a of the core 16, into which the spring pin 22 is pressed so as to constantly restrain the upstream-end 24 c of the compression spring 24.

Instead of the above copper alloy having a resistance against sulfur, the surface of the spring pin 22 may be covered with material which has excellent characteristic in a resistance against sulfur. The material for covering the spring pin 22 may not be limited to the above copper alloy having a resistance against sulfur, but may be a Ni—P alloy. With a Ni—P alloy, it is possible to easily form a stable film by plating. In this case, the material with which the spring pin 22 is made may be selected from group of materials having the desired rigidness or other characteristic as desired in the spring pin 22.

The specific embodiments of the present invention are described above, but these merely illustrate some possibilities of the invention and do not restrict the claims thereof. The art set forth in the claims includes various transformations and modifications to the specific embodiment set forth above.

Furthermore, the technical elements disclosed in the present specification or figures may be utilized separately or in all types of conjunctions and are not limited to the conjunctions set forth in the claims at the time of filing of the application. Furthermore, the art disclosed in the present specification or figures may be utilized to simultaneously realize a plurality of aims or to realize one of these aims. 

1. A fuel injection valve, comprising: a main body that comprises a fuel passage and a fuel injection opening formed at a downstream-end of the fuel passage; a valve member that is disposed in the fuel passage, and configured to move between a first position in which the valve member closes the fuel injection opening and a second position in which the valve member opens the fuel injection opening; a compression spring that is disposed in the fuel passage, and configured to restrain the valve member toward the first position; and a spring pin that is tightly inserted into the fuel passage, and configured to keep the compression spring within the fuel passage, wherein a surface of the spring pin has a resistance against sulfur.
 2. A fuel injection valve as in claim 1, wherein the spring pin is made of material having a resistance against sulfur.
 3. A fuel injection valve as in claim 1, wherein the spring pin is made of a copper alloy having a resistance against sulfur.
 4. A fuel injection valve as in claim 1, wherein the spring pin is made of a copper alloy containing at least one of nickel, silicon, aluminum, and chromium, and the at least one of nickel, silicon, aluminum, and chromium is included in the copper alloy by at least 5 percent by weight.
 5. A fuel injection valve as in claim 1, wherein the spring pin is made of albata.
 6. A fuel injection valve as in claim 1, wherein the surface of the spring pin is covered with material having a resistance against sulfur.
 7. A fuel injection valve as in claim 6, wherein the surface of the spring pin is covered with a Ni—P alloy.
 8. A fuel injection valve as in claim 1, wherein an exterior surface of the spring pin is roughened.
 9. A fuel injection valve as in claim 8, wherein the exterior surface of the spring pin is roughened by shot peening treatment. 